biology homeostasis 4.5.1 + nervous system 4.5.2.1

homeostasis

the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes

what does homeostasis do?

maintains optimal conditions for enzyme action and all cell functions

in the human body, “all enzyme action and cell functions” include the control of:

• blood glucose concentration

• body temperature

• water levels

these automatic control systems may involve nervous responses or chemical responses. all control systems include:

• cells called receptors, which detect stimuli

• coordination centres (such as the brain, spinal cord, and pancreas) that receive and process information from receptors

• effectors, muscles or glands, which bring about responses which restore optimum levels

the nervous system …

… enables humans to react to their surroundings and to coordinate their behaviour

information from receptors passes along neurones as …? to the …?

• electrical impulses

• CNS

what is the CNS and what does it do?

it is the brain and spinal cord; it coordinates the response of effectors which can be a) muscles contracting or b) glands secreting hormones

reflex arc?

stimulus → receptor → coordinator → effector → response

what do each of the structures in a reflex arc do?

• receptor detects a stimulus

• coordinator receives information from receptors about a stimulus and processes it to initiate a specific response

• effector produces a response

reflex actions are …? they do not involve the …?

• automatic and rapid

• conscious part of the brain